1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for a location update in a wireless communication system.
2. Related Art
The institute of electrical and electronics engineers (IEEE) 802.16e standard was adopted in 2007 as a sixth standard for international mobile telecommunication (IMT)-2000 in the name of ‘WMAN-OFDMA TDD’ by the ITU-radio communication sector (ITU-R) which is one of sectors of the international telecommunication union (ITU). An IMT-advanced system has been prepared by the ITU-R as a next generation (i.e., 4th generation) mobile communication standard following the IMT-2000. It was determined by the IEEE 802.16 working group (WG) to conduct the 802.16m project for the purpose of creating an amendment standard of the existing IEEE 802.16e as a standard for the IMT-advanced system. As can be seen in the purpose above, the 802.16m standard has two aspects, that is, continuity from the past (i.e., the amendment of the existing 802.16e standard) and continuity to the future (i.e., the standard for the next generation IMT-advanced system). Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining compatibility with a mobile WiMAX system conforming to the 802.16e standard.
There is ongoing development on the IEEE 802.16p standard optimized for machine-to-machine (M2M) communication based on the IEEE 802.16e standard and the IEEE 802.16m standard. The M2M communication can be defined as an information exchange performed between a subscriber station and a server or between subscriber stations in a core network without any human interaction. In the IEEE 802.16p standard, there is an ongoing discussion on enhancement of medium access control (MAC) of the IEEE 802.16 standard and a minimum change of an orthogonal frequency division multiple access (OFDMA) physical layer (PHY) in licensed bands. Due to the discussion on the IEEE 802.16p standard, a wide area wireless coverage is required in the licensed band, and a scope of applying automated M2M communication can be increased for an observation and control purpose.
When accessing a network, requirements demanded by many M2M applications are significantly different from requirements for human-initiated or human-controlled network access. The M2M application can include vehicular telematics, healthcare monitoring of bio-sensors, remote maintenance and control, smart metering, an automated service of a consumer device, etc. The requirements of the M2M application can include very lower power consumption, larger numbers of devices, short burst transmission, device tampering detection and reporting, improved device authentication, etc.
A user equipment (UE) can perform a location update when a specific condition is satisfied. When performing the location update process, a base station (BS) transmits information on a mobility access classifier and reattachment zone of the UE to an authenticator in a network entry stage. The mobility access classifier indicates a fixed UE or a nomadic UE. The reattachment zone indicates a list of BSs accessible by the fixed UE or the nomadic UE. The UE transmits an AAI-RNG-REQ message to the BS to perform the location update. The BS transmits an R4_LU_Req message to an anchor paging controller (PC) access service network (ASN). The anchor PC ASN receives the R4_LU_Req message and confirms information on the mobility access classifier and reattachment zone of the UE. If an identifier (ID) of a BS on which the UE intends to perform the location update is not included in the list of the BSs of the reattachment zone, the R4_LU_Req message is transmitted to the BS so that the UE performs an initial network reentry with respect to the BS instead of the location update.
In addition, in the paging process, the anchor PC ASN confirms the information on the mobility access classifier and reattachment zone of the UE before transmitting a paging announcement. If the UE is the fixed or nomadic UE, the anchor PC ASN can transmit the paging announcement only for a BS included in the list of the reattachment zone.
Meanwhile, an M2M device can perform the location update similarly to a typical UE. There may be a need for a more effective location update method according to a characteristic of an M2M application to which the M2M device is applied.